Have you ever noticed that you had a reaction to an event or person that made you think “Gosh, I must be overreacting,” or, “Wow, I wonder where those feelings came from,” because in your mind the feelings didn't seem to fit the occasion? For example, in a couple I see, whenever Marsha (the wife) worries about their child, Laura, Stanley (an otherwise loving and sensitive husband) gets annoyed and responds, “Oh, here we go again!” Of course, Marsha doesn't take kindly to that remark and it interferes in their relationship. But Stanley can then reflect, and say, “I don't know why I get like that; she has every right to have these feelings, and I actually respect her for them; I just can't help it.” Or, in another example, let's say our cell phone goes through a dead zone, our call is dropped, and even though nothing that urgent was being discussed and the call wasn't with somebody telling us we won the lottery, or anything on that level, and our day was basically going well, and we're not a rage-aholic by nature; nevertheless we find ourselves suddenly having a tantrum and wanting to drop kick the phone across the street. Intellectually our reaction just doesn't make sense and we're in the position of feeling really upset on one level, (feelings), puzzled on the other (thoughts), and split within our self.
This is what happens to we humans (animals don't have that problem—they just get to have feelings without accompanying thoughts or judgments) when something emotionally important from our past is triggered by a similar event or confluence of events, or feelings, sensations, or even a smell. If we desist from wrecking our phone, apologize to our significant other, just let the feeling pass and go about our business, it's not a big deal. It becomes a big deal when we repeat the same thing over and over and find we can't control it, or act on it in a way we regret, and then it's useful to do a little self-analysis. Sometimes just noticing it or sharing it with a trusted friend is good enough and we can change our behavior. When that's not working, talking in therapy can help. On an extreme level, in the case of PTSD, when we are run by an old trauma, therapies like EMDR (Eye Movement Desensitization and Reprocessing) can help. What needs to happen is to have our natural observing abilities connect with the old (and it can be very old, it doesn't matter how many years have gone by) memory and the old feelings associated with it in the context of a healing process. Then we begin to make more sense to ourselves and to feel integrated.